This invention relates to polyfunctional urethane- or urea-containing oligomers, their methods of synthesis, and polymers and compositions prepared therefrom.
One of the groups of polymers with the most attractive combination of properties that is currently used in the plastics, paint, adhesives, etc. industries are polyurethanes. The unique complex of polyurethane properties is created by the ability of the urethane groups to participate in strong intermolecular interactions.
The superior properties of polyurethanes are caused by the unique characteristics of the urethane group. Most of the other classes of polymers do not have similar complex of positive features as polyurethanes. However, the properties of the other currently manufactured polymers (from elastomers to plastics) could be significantly improved by introduction of the urethane group into the molecules of polymer.
The intention to combine the polyurethanes advantages with the inherent properties of other resins has led to the synthesis of urethane-epoxies, for example as described in Russian Patent No. 287,589 and U.S. Pat. Nos. 2,830,038, 3,984,376, 4,520,185, and 5,484,853; urethane-acrylics and urethane-methacrylics, for example as described in U.S. Pat. Nos. 3,850,770, 4,131,600, 4,133,723, 4,153,778, 4,246,391, 4,330,657, 4,339,566, 4,507,458, 4,587,201, 4,605,723, 5,006,436, and 5,616,630; urethane-alkoxysilanes, for example as described in U.S. Pat. Nos. 4,374,237, 4,555,561, and 4,857,623; and urethane-vinyls and allyls, for example as described in U.S. Pat. Nos. 3,719,638, 4,119,510, and 5,580,947.
However, the disclosed in the available literature amount of types of functional groups combined with urethanes in single oligomeric molecules is limited to the above-mentioned compounds. The range of the described products is very narrow.
Despite the obvious advantages of the described products, they are not widely used in the industrial applications. The limited amount of the utilized functional groups, difficulty in the adjustment of physical and chemical properties of products and complex and limited methods of production of described in available literature compounds lead to limitations on the range of properties of both produced oligomers and the final products obtained after their curing.
In a first aspect, this invention provides oligomers of formula (1)
B(xe2x80x94R1xe2x80x94C(O)xe2x80x94NHxe2x80x94R2xe2x80x94R3)nxe2x80x83xe2x80x83(1),
where:
B is a backbone selected from the group consisting of polyesters, polyethers, polyolefins, polybutadienes, polysiloxanes, carbohydrates, polyacrylates, and mixtures and copolymers thereof;
each R1, which may be the same or different, is selected from xe2x80x94Oxe2x80x94,xe2x80x94Sxe2x80x94, and xe2x80x94N(R5)xe2x80x94, where R5 is selected from hydrogen or a monovalent organic radical; each R2, which may be the same or different, is a bivalent organic radical; each R3 is a group selected from an isocyanate group or a group of formula (2):
xe2x80x94NHxe2x80x94C(O)xe2x80x94R1xe2x80x94R4xe2x80x94ƒxe2x80x83xe2x80x83(2),
xe2x80x83where:
each R1 is as defined above,
each R4 is a bivalent radical selected from the group consisting of bivalent aliphatic, cycloaliphatic, aromatic, substituted aliphatic, substituted cycloaliphatic, and substituted aromatic radicals, and bifunctional polyesters, polyethers, polyolefins, polybutadienes, polysiloxanes, and polyacrylates;
ƒ is a functional group, and
n is an integer from 2 to 10;
in which at least two different R3 groups are present in the oligomer, and if one R3 group is isocyanate, then at least three different R3 groups are present in the oligomer.
In a second aspect, this invention provides mixtures of oligomers in which at least one oligomer is one of the above oligomers.
In a third aspect, this invention provides methods to produce the above oligomers.
In a fourth aspect, this invention provides polymers prepared from the above oligomers, alone or in combination with other urethane oligomers.
In a fifth aspect, this invention provides compositions such as adhesives, sealants, coatings, and composites containing these oligomers and polymers prepared therefrom.
The herein-described and claimed products and methods of their synthesis substantially widen the range of urethane- and urea-functional oligomers, expand their properties, provide mechanisms for the adjustment of these properties, and ease the production of oligomers.
A xe2x80x9cbackbone carrierxe2x80x9d is an oligomer of formula (3):
Bxe2x80x94(R1H)nxe2x80x83xe2x80x83(3),
where:
B, R1, and n are as defined previously.
xe2x80x9cFunctional groupsxe2x80x9d (FGs), ƒ, are groups of two types:
(1) groups capable of reaction by polymerization or polycondensation; and
(2) groups that provide desired changes in the physical and/or chemical properties of the final product.
Suitable functional groups ƒ as described in this invention are selected from reactive functional groups, including but not limited to epoxy (oxirane), acrylate, methacrylate, mercaptan, vinyloxy, allyl, carboxyl, ketone, nitrile, organic nitrate, primary, secondary and tertiary amine, organic peroxide, alkoxysilane, carbonate, aromatic, saturated and unsaturated organic radicals, halogenated organic radicals, heterocyclic radicals, and the like; catalytic, photoinitiator or stabilizer functional groups including but not limited to tertiary amines, imidazoles, organic peroxides, metalloorganic and heterocyclic radicals, hydroxyketones, hydroquinones, and the like; and physical property-modifying functional groups including but not limited to aliphatic, cycloaliphatic and aromatic, saturated and unsaturated organic radicals, halogenated organic radicals, and the like.
Functional groups ƒ are attached to the backbone of the oligomers by the use of compounds called xe2x80x9cfunctional group (FG) carriersxe2x80x9d.
An xe2x80x9cFG carrierxe2x80x9d is a compound of formula (4):
ƒxe2x80x94R4xe2x80x94R1Hxe2x80x83xe2x80x83(4),
where
ƒ, R1, and R4 are as defined previously.
A xe2x80x9cpolyfunctional reactive urethane- or urea-containing oligomerxe2x80x9d (PRUO) is a compound of the formula:
B(xe2x80x94R1xe2x80x94C(O)xe2x80x94NHxe2x80x94R2xe2x80x94R3)nxe2x80x83xe2x80x83(1),
where:
B is a backbone selected from the group consisting of polyesters, polyethers, polyolefins, polybutadienes, polysiloxanes, carbohydrates, polyacrylates, and mixtures and copolymers thereof;
each R1, which may be the same or different, is selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, and xe2x80x94N(R5)xe2x80x94, where R5 is selected from hydrogen or a monovalent organic radical;
each R2, which may be the same or different, is a bivalent organic radical;
each R3 is a group selected from an isocyanate group or a group of formula (2):
xe2x80x94NHxe2x80x94C(O)xe2x80x94R1xe2x80x94R4xe2x80x94ƒxe2x80x83xe2x80x83(2),
xe2x80x83where:
each R1 is as defined above,
each R4 is a bivalent radical selected from the group consisting of bivalent aliphatic, cycloaliphatic, aromatic, substituted aliphatic, substituted cycloaliphatic, and substituted aromatic radicals, and bifunctional polyesters, polyethers, polyolefins, polybutadienes, polysiloxanes, and polyacrylates;
ƒ is a functional group, and
n is an integer from 2 to 10;
in which at least two different R3 groups are present in the oligomer, and if one R3 group is isocyanate, then at least three different R3 groups are present in the oligomer.
The PRUOs are the oligomers of this invention. They are compounds that have multiple and diverse useful properties. These properties are determined by the type, functionality and length of the backbone, the type of linkages (urethane or substituted urea), and the types, combinations and relative amounts of functional groups on the PRUO.
In the preferred compounds of this invention:
B is a backbone selected from polyesters (for example, poly(neopentyl glycol adipate), alkyd resins, polyethylene glycol maleate, and the like), polyethers (for example, polyethylene glycol (polyoxyethylene), polyoxypropylene, polytetramethylene glycol, and the like), polyolefins (for example, castor oil, low molecular weight polyethylenes, hydrogenated polybutadiene, and the like), polybutadienes (for example, cis- and trans-polybutadienes, and acrylonitrile-polybutadiene copolymers, and the like), polysiloxanes (for example, polydimethylsiloxanes, polydiethylsiloxanes, polydiphenylsiloxanes, polyphenylmethylsiloxanes, and the like), carbohydrates (dextrins, cyclodextrins, cellulose ethers, and the like), polyacrylates (polyacrylates such as polyethylacrylate, polymethacrylates such as polymethylmethacrylate, styrenated polyacrylics, and the like), copolymers, such as block copolymers, and mixtures of two or more of the above.
R1 is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94N(R5)xe2x80x94, preferably xe2x80x94Oxe2x80x94.
R2 is the residue of a diisocyanate molecule, for example, 2,4-toluylene, 2,6-toluylene, tetramethylene, hexamethylene, trimethylhexamethylene, isophorone, and the like.
R4 is bivalent linear or branched alkyl of up to 30 carbon atoms, aryl of up to 10 carbon atoms, each optionally substituted with one or more non-interfering substituents, xe2x80x94(C2H4O)xxe2x80x94 where x is up to 10, xe2x80x94(C3H7O)yxe2x80x94 where y is up to 15, hydrogenated polybutadiene of MW less than 4000, polycaprolactone, and the like.
R5 is hydrogen or a monovalent linear or branched aliphatic or olefinic (by which is included any degree of unsaturation) or aromatic hydrocarbon radical of up to 50 carbon atoms, preferably up to 20 carbon atoms, optionally substituted with one or more non-interfering substituents.
Typically, at least a portion of the functional groups ƒ are epoxy groups and/or acrylate or methacrylate groups.
The extent of crosslinking of the oligomer may be varied by regulating the proportion of the R3 groups that are isocyanate.
The numerous possibilities of combinations of these factors allow only to provide a few descriptions of the possible oligomers (PRUOs) and their uses. Combinations of various functional groups in one oligomeric molecule allow, among other possibilities, to:
(1) In the case of a PRUO containing primarily acrylic groups and up to 10% of a ketone group that serves as an effective photoinitiator of radical polymerization, to increase the effectiveness of photopolymerization under the influence of visible and/or UV light, due to a reduction in the order of the catalytic reaction from second to first order (by virtue of the catalyst being a part of the oligomer). The possibility of migration of the catalyst from the cured material is completely eliminated.
(2) In the case of a PRUO containing primarily acrylic groups and up to 10% of an organic peroxide group that serves as an effective catalyst of radical polymerization, to reduce the order of the catalytic action reaction from second to first order, thus diminishing the necessary amount of peroxide and producing a self-curable material. The possibility of migration of the catalyst from the cured material is completely eliminated.
(3) In the case of a PRUO containing primarily epoxy groups, the addition of a noticeable (up to 40%) amount of aliphatic FGs allows a significant decrease in the viscosity of the synthesized oligomer, and increases its chemical resistance and compatibility
(4) Both urethane-epoxies with free isocyanate functionality and epoxy-based MIFRI that utilize glycidol as the FG carrier provide a significant additional benefit, in that upon heating, they can cure without a separate hardener. Their self-curing is based on the intramolecular rearrangement of the urethane-epoxy groups that occurs upon the heating of the system to 80xc2x0 C. and above with the formation of a six-membered oxazine structure and a hydroxyl group, or with the formation of a five-membered oxazolidone structure and a hydroxyl group. The ratio between the two type of the heterocycles depends on the type and length of the R groups in the oligomer, however, usually 65%-70% of the oxazine and 35%-30% of the oxazolidone structures are formed.
(5) Compounds containing the urethane-epoxy and isocyanate groups can be used as very effective one-package thermally cured adhesives. The hydroxyl groups formed as the result of this intramolecular rearrangement are also reactive with free isocyanate groups that are either attached to the PRUO, or may be added to it in the form of various polyisocyanates. This mechanism provides extra cross-linking to the cured PRUO.
PRUOs can be synthesized in one stage by mixing together three types of precursors:
at least one backbone carrier;
at least one diisocyanate having unequal reactivity of the isocyanate groups, such as, for example, isophorone diisocyanate, 2,4-toluylene diisocyanate, or trimethylhexamethylene diisocyanate; and
at least two different FG carriers.
It is preferred that the reactivity of the R1H groups of the FG carriers and backbone carriers towards the isocyanate groups of the diisocyanate used also shall be unequal.
There are three methods to produce PRUOs in two stages.
(1) Two-stage synthesis of PRUOs through a monoisocyanate-functional reactive intermediate (MIFRI)
The first method requires the production of the monoisocyanate-functional reactive intermediate (MIFRI) as the first stage of the process.
(a) Production of the MIFRI through diisocyanates having isocyanate groups of unequal reactivity
In order to produce a MIFRI, a diisocyanate having isocyanate groups of unequal reactivity, such as isophorone diisocyanate, 2,4-toluylene diisocyanate (2,4-TDI), or trimethylhexamethylene diisocyanate is mixed in 1:1 molar ratio with a FG carrier. For example, the reaction of 4-amino-tetramethylene-tri(ethoxy)-silane with 2,4-TDI produces a substituted urea bifunctional adduct intermediate with isocyanate and tri(ethoxy)silane groups. As the isocyanate group in the para-position is much more active than the isocyanate group in the meta-position, the chance of formation of a product with two tri(ethoxy)silane groups is practically eliminated.
(b) Production of a MIFRI through diisocyanates having isocyanate groups of equal reactivity
If the diisocyanate has isocyanate groups of equal reactivity, such as 2,6-toluylene diisocyanate (2,6 TDI), diphenylmethane diisocyanate (MDI), aliphatic diisocyanates, etc., it is impossible to produce a MIFRI by adding FG carriers directly to the diisocyanate in a 1:1 molar ratio. In this case some the product will have two FGs, some will have one FG, and some will have none.
The only described method of producing these types of compounds is to use a huge excess of diisocyanates in the reaction mixture, to ensure that the primary product is the 1:1 product. In this case the synthesis is followed by the removal of excess diisocyanates by distillation. This technology is very expensive and cumbersome, and inevitably leaves some unreacted diisocyanate in the product.
This invention allows synthesizing a MIFRI by conducting the reaction in a non-polar solvent. Both diisocyanates and most FG carriers are soluble in non-polar solvents not containing proton-acceptor groups (for example, aliphatic hydrocarbons such as hexane).
However, after the first reaction between the diisocyanate and FG carrier is complete and a MIFRI is formed, the MIFRI reaction products (with the newly-formed very polar urethane or substituted urea groups) are insoluble in the non-polar solvents and may be removed from the reaction mixture by phase segregation, thus eliminating the possibility of reaction between the MIFRI and another molecule of FG carrier.
A mixture of two or more of the synthesized MIFRIs is later reacted with the backbone carrier producing a desired PRUO.
(2) Two-stage Synthesis of PRUOs through functional group-terminated compounds containing the uretidindione structure
At the first stage of the synthesis, a diisocyanate dimer (a diisocyanate-terminated compound that contains a thermally unstable uretidindione structure and under the influence of elevated temperature decomposes to release two diisocyanate moleculesxe2x80x94many such diisocyanate dimers are commercially available) is reacted with two or more FG carriers at a temperature below that at which the uretidindione structure decomposes (for example, not exceeding 50xc2x0 C.), thereby forming a mixture of functional group-terminated compounds containing the uretidindione structure. The resulting compounds react with the backbone carrier at an elevated temperature (i.e. at a temperature above that at which the uretidindione structure decomposes) through the combination of isocyanate groups released by the break-up of the uretidindione structure and the isocyanate-reactive terminal groups of the backbone carrier.
(3) Two-stage Synthesis of PRUOs through an isocyanate-terminated prepolymer
The first stage of the synthesis is production of an isocyanate-terminated prepolymer having a functionality xe2x89xa72. Such syntheses are well-described in the literature, and commercial prepolymers are widely available. At the second stage the synthesized or commercially obtained prepolymer is reacted simultaneously with two or more of the FG carriers, producing a PRUO with the desired properties.